This invention relates to motor vehicles incorporating deployable roll bar assemblies and particularly to convertible motor vehicles having a rear window made of glass.
Applicants co-pending application EP 04254627.7 describes a deployable roll bar assembly capable of shattering a vehicle's rear window on deployment. The assembly includes a hollow inverted U-shaped roll bar which is retained in a housing by a spring-loaded mechanism. The housing may be fixed to a rear bulkhead of the vehicle. The bar is fitted with one or two pins on its upper surface. The pins are fixed to the roll bar by means of a threaded joint. A protruding part of the pin may have a conical, frusto-conical, or domed shape. Such shapes have been found to break a glass window satisfactorily, causing it to shatter into small pieces. The protruding part of the pin is made from a hard material e.g. tungsten carbide.
When a vehicle motion sensor detects that rollover of the vehicle is imminent, the spring-loaded mechanism is released. Consequently, the roll bar is rapidly deployed upwards towards the rear window, whereupon at least one of the pins strikes the window causing it to shatter into many fragments. Once the roll bar is deployed to its fullest extent, it locks in position just beyond the roof line and clear of the head of any occupants, thus affording the necessary protection.
The assembly described in EP 04254627.7 further provides an item of trim, which may be frangible or removable, and located over the roll bar's upper surface to prevent the pins from causing any damage to passengers or items of clothing or luggage. In the case where a frangible item of trim is used, the roll bar is required to break through the trim item as it progresses on its way towards the rear window. Thus, energy is expended in breaking the trim item. In the alternative case where a removable item of trim is used, the roll bar is required to push the trim item out of the way as it progresses towards the rear window. This puts design constraints on the trim item and on the vehicle interior as it must be ensured that the trim item will not become lodged between the roll bar's upper surface and any part of the vehicle in a way that could prevent the pin from hitting the rear window. Furthermore, as in the case off the frangible trim item, energy is expended in forcing the trim item out of the way. This puts an additional performance requirement on the roll bar release mechanism.
Hence it would be advantageous to provide a deployable roll bar and trim assembly which did not suffer from the above-mentioned drawbacks.